In recent years, the fact that a microwave accelerates a chemical reaction was found and interest in a chemical reactor using a microwave is increasing in fields such as biochemistry. A batch processing device, for example, a kind of kitchen type microwave oven, is currently mainstream device in such a microwave apparatus for accelerating a chemical reaction or heating, the batch processing device performs a treatment by using a test tube or a flask containing a liquid to be treated. However, the batch processing device is limited in throughput capacity and thus, a flow type device in which a flow channel is formed and irradiated with a microwave while a liquid to be treated flows therethrough is under study (see Patent Document 1).